1. Technical Field
The present invention generally relates to printed circuit boards, and particularly relates to a process for manufacturing a printed circuit board having different thicknesses in different areas.
2. Discussion of Related Art
Printed circuit boards (PCBs) having different thicknesses in different areas have been widely developed. The PCB usually includes different plurality of layers in different areas, i.e., has a thick portion with a number of layers and a thin portion with fewer layers. The thick portion has a higher circuit density whilst the thin portion exhibits higher flexibility.
FIG. 9 shows a structure of a PCB 100 having different thicknesses in different areas. The PCB 100 includes a first substrate 110, a binder layer 130 and a second substrate 120. The PCB 100 has an opening 101 passing through the second substrate 110 and the binder layer 130. The first substrate 110 has an electrical traces layer 111. A mounting area 112 of the electrical traces layer 111 for mounting electronic elements is exposed via the opening 101.
FIGS. 10˜11 show a process for manufacturing the PCB 100. As shown in FIGS. 10˜11, a first substrate 110 including an electrical traces layer 111, an binder layer 130 having an opening 131 and a second substrate 120 are provided. The second substrate 120 includes a base 121 and a conductive layer 122 formed on the base 121. As shown in FIG. 11, the second substrate 120, the binder layer 130 and the first substrate 110 are laminated, and a portion 120a of the second substrate 120 corresponding to the opening 131 is removed using a laser cutter or a milling cutter.
When the base 121 is made of glass fibers and polymer resin, i.e., the second substrate 120 is a rigid, the second substrate 120 may have different thickness in different areas. It is known that a cutting depth of a laser cutter is in direct proportion with a cutting energy of the laser cutter. To cut off the portion 120a without damaging the mounting area 112, a cutting energy of the laser cutter must be adjusted according to a practical thickness of the second substrate 120 where the laser is applied on. However, it is difficult to precisely control the cutting energy of the laser cutter. Thus, during cutting off the portion 120a, the mounting area 112 may subject to damages cause by the laser cutter.
What is desired, therefore, is a method for manufacturing a printed circuit board having different thicknesses to overcome the above-described problems.